export default class UploadAdapter {
    constructor( loader, options ) {
        this.loader = loader;
        this.options = options;
    }

    upload() {
        return this.loader.file
            .then( file => new Promise( ( resolve, reject ) => {
                this._initRequest();
                this._initListeners( resolve, reject, file );
                this._sendRequest( file );
            } ) );
    }

    abort() {
        if ( this.xhr ) {
            this.xhr.abort();
        }
    }

    _initRequest() {
        const xhr = this.xhr = new XMLHttpRequest();
        
        xhr.open( 'POST', this.options.upload.uploadUrl, true );
        xhr.responseType = 'json';
    }

    _initListeners( resolve, reject, file ) {
        const xhr = this.xhr;
        const loader = this.loader;
        const genericErrorText = `Couldn't upload file: ${ file.name }.`;

        xhr.addEventListener( 'error', () => reject( genericErrorText ) );
        xhr.addEventListener( 'abort', () => reject() );
        xhr.addEventListener( 'load', () => {
            const response = xhr.response;
            if ( !response || response.code == 0 ) {
                return reject( response && response.code == 0 ? response.message : genericErrorText );
            }
            resolve( {
                default: response.data.src
            } );
        } );

        if ( xhr.upload ) {
            xhr.upload.addEventListener( 'progress', evt => {
                if ( evt.lengthComputable ) {
                    loader.uploadTotal = evt.total;
                    loader.uploaded = evt.loaded;
                }
            } );
        }
    }

    _sendRequest( file ) {
        // Set headers if specified.
        const headers = this.options.upload.headers || {};
        const extendData = this.options.upload.extendData || {};
        // Use the withCredentials flag if specified.
        const withCredentials = this.options.upload.withCredentials || false;
        const uploadName = this.options.upload.uploadName || 'file';
        for (const headerName of Object.keys(headers)) {
            this.xhr.setRequestHeader(headerName, headers[headerName]);
        }
        this.xhr.withCredentials = withCredentials;
        const data = new FormData();
        for (const key of Object.keys(extendData)) {
            data.append(key, extendData[key]);
        }
        data.append( uploadName, file );
        this.xhr.send( data );
    }
}

export function CustomUploadAdapterPlugin( editor ) {
    editor.plugins.get( 'FileRepository' ).createUploadAdapter = ( loader ) => {
        return new UploadAdapter( loader, editor.config._config );
    };
}